Sanding drum



C. BECKER SANDING DRUM July 16, 1929.

Filed Jan. 13, 1926 Patented July 16, 191219.

units srAIs CHRISTIAN BECKER, OI"l RocK'FoRn, ILLINOIS, AssIGNoR To MATTISON ivIAciIINn WORKS, or RocKroRn ILLINOIS, A CORPORATION or ILLINOIS.

SANDING- DRUM.

Application filed January 13, 1926. Serial No. 80,8715.

This invention relates generally to sanding' Vthe paper- ,stretching and also because of thel decrease' in thickness ofthe stretched felt, considerable slack is produced in the paper Wound On the drum. The present invention aims to provideautoinatic and independent tensioning means for thepadding and for the paper in order to maintain'substantially uniform conditions of tension throughout the use of the drum. Not only is the tension equalized throughout the use of the drum, but the felt is prevented from bunching up under the paper to make the .sanding roll eccentric. f

vAnother object of the invention is to provide a paper tensioning device which pulls upon the paper substantially tangentially of the drum.

Still another object of the invention is the provision ofy spring operated tensioning `devices and of vcaml means for releasing and positively holding vsaid devices. Y

Another object is to so relate a sheet clamping means and a sheet tensioning means that onel is automatically rendered inoperative when the other is made inoperative.

Still another object is to yprovide sheet holding devices which can be duplicated at intervals along an elongated drum with al common means for rendeiing saidfduplicate structures inoperative.

Still other and ancillary objects and ad# vantages of the invention will be apparent from the following description of an illus` trative land exemplary embodiment of-,the invention as shown in the accompanying drawings in which:

Figure 1 is a longitudinal cross section of a sanding drum,V partly in elevation.

Fig. 2 is a transverse section along the l line 2.-2ofFig. 1. y

Fig. 3 is a transverse section along the line 3-3 of Fig. 1. f Fig. 4 is a plan view in section along the line 4-4 of Fig. 2.

Fig. 5 is a detailed view of the paper ten'- V sioning device.

Although the following description refers in detail to the structure illustrated' in the drawings, it is to be understood that theinvention is not to be construed as limited to the'construction herein vdisclosed and described. To the mind of one' skilledin the 'ai-t7 other arrangementsl of the parts and other Vembodiments of the invention Awill doubtlessly occur and such constructions and arrangements are herein contemplated by the invention as expressed in the appended `7() claims. 1

In the drawings there is shown a device comprising a longitudinally splitcylindrical drum which may have any desired .lengthf According to its length it has a suiicient number of duplicate structures or groups ofv suoli structures which `serve to fastenand tension a padding placed over the druin surface and a sheet of abrasive material placed'/ over said padding. The endsof the padding and of the abrasive sheet are preferably secured within the periphery ofthe drum and.

enter through the longitudinal gap provided therein. The advancing ends of the abra-1 to keep the padding andthe paper always,l

taut irrespective of the stretching,.creeping or loosening of the sheets as the drum is used. It is obvious that there is tendency forthe paper or padding to stretch or creep toward thetail kend' as the sheet moves relatively to' i the work and lconsequently tensioning devices are preferably positioned to operateon the tailrendsr of the padding and the paper.

A drum 10 is indicated which is preferably p made of cast iron, being constructed with transverse webs 11 spaced apart within the drum and provided lwith supporting bearings 12 fora mounting shaft 13. Screws 14 hold the drum rigid tothe shaft. The drum'has at one side by an edge 16 of the drum body and on the other sideby a cast iron structure an open seam orlongitudinal gap 15 defined n 17 substantially triangular and prismatic in shape. This structure is a removable section of the drum and has an arcuate surface 18 forming a section of the drum periphery, and has also an inwardly directed face or flange 19 recessed as shown at 20. The druin section 17 is-secured to the drum proper by screws 21 entering the webs 11.

The section 17 is preferably made to provide the advancing edge of the gap 15, the drum being rotated in the direction of the arrow. There is secured to the flange 19, a sheet of padding such as felt 22 and a sheet of Vabrasive paper 23 outside of the padding. The padding is secured by a screwed cleat o-r strip 24 clamping it to a ledge 25 formed inv the flange 19. The free end'otl the felt after passing around the drum again enters the gap 15 and passes over the edge 1G where 1t is secured byni'eans later to be described. The

" paper strip23 is similarly placed over the entire drum, but both edges are held against an abutment provided by the flange 19 by a clamping bar 26 which enters the recess 20. Thus' the abrasive paper spans the gap from the edge 16 to the flange 19, the spanning portion of the paper ybeing inwardly directed at a slight angle to tangent of the drum periphery. V Y

To enable one to replace the paper readily the clamping bar 26 is mounted for actuation away from the recess by a simple mechanical structure. In Fig. 2 the bar 26 is shown mounted on an arm 27 of a lever having other arms 28 and 29 and turning on a pivot shaft 30 extending parallel to the axis of the drum.

A heavy spring 31 is interposed vbetween the arm 28 and 'the' drum 10 to hold the bar 26 tightly in the recess 20. The arm 29 crosses a rock shaft 32 parallel to the shaft. 30 and mounted in the webs 11.Y The shaft 32 a cam Surface acting on the arm 29 to move the lever. Thecam surface is formed by flatteningthe shaft substantially to a semi-circular cross section as shown at 33. The shaft 32 has V*a squaredend 84 to which a suitable wrench friction thereon.

or key `may be applied for turning the shaft to unclamp the paper, the cam 33 holding the clamping means for the felt is made movable and serves not only to hold the felt against the drum but also to move with it as it creeps and thereby to keep it under an even tension as it is elongated in use. The tail end of the felt is folded under the drum edge 16 .which isc preferably made rounded to minimize the On the underside of the edge 16 the felt is clamped by a movable bar 35"ha'ving saw-like' gripping teeth 3G. The

marne bar 35 is carried on an arm 37 of a lever having other arms 38 and 39 and turning on a shaft 40 paralleling the axis of the drum. A spring 41 is` interposed between the arm 38 and the drum 10 to force the bar 35 in a direction to pull the felt taut. The arm 39 crosses a cam shaft 42 having a iiattened cam surface 43 and a squared end 44similar to the other shaft 32.

As the paper stretches or loosens in use and as the padding decreases in thickness when it stretches, there is .thus produced considerable increasing slack in the paper which should be taken up. 'It isV highly desirable that the slack be taken'up with as little friction as possible. For this reason it is pulled substantially in a line deviating but slightly from -a tangent vto the cylindrical surface. Thus there is avoided considerable pressure and friction at the edge 16. Such pressure also would act to bind the felt more tightly to the edg-eand hinder its tensioning means from taking up the felt slack.

i Much of thevstructure heretofore described has been utilized 'in providing a tensioning means for the paper. Referring to Fig. 5 the initial position of the paper is shown as a dotted line, the paperl spanningthe gap from the edge 16 to the recess 20 at a slightr having other arms 47 and'48 and turning on Y the above named shaft 30. A spring 49 is placed-between the arm 47 and thedruin 10 to exert a tensioning force on the paper. T'he tensioning bar 45 swings about the shaft'BO from the dotted lineposition of Fig. 54 through the full line'operat'ive position Yshovvn'in Fig. 3, and may ni'ove to the `limiting 'position shown 'in full lines jin Fig. `5. The paper tensioning means is thus normally pressed against the paper *byxits spring 49. Asa means to' render inoperative the tension bar and to hold it in van out-of-the-way position for replacing the abrasive'sheet,l a cam is pro'- vided to' act upon the arm 48. The arm Yis positioned sotliat a yflat spot 50 formed fas a cam on the 'shaft 40 pivoting the felt tensioning lever' serves this purpose. Consequently the pivot shaft 40 is rotatably'mounted in bearingsalong the webs 11 aIdis provided with a squared end 51.

The cylindrical portion of the drum dianietricallyr opposite the gap 15 lis constructed relatively thick as'indicated at 52to counterbalance the Weight of the holding andtensioningv structures. Thein'ner surface of this portion is made'flat sothat an additionalbalancing Weight ina'y be secured vthereto to .perfect the balance for high speed operation.'

' l,Referring to Figure 1 it lwill be seen that a long drum may. have a vplurality of duplicate group above described in detail. The various cam shafts 30, 40 and 42 therefor preferably extend the whole length of the drum so that of the drum. l Y In preparing to use the drum one places the they are common to each of the duplicate devices, thusk permitting all similar devices to be operated simultaneously from one end padding about the drum, first securing the leading end to the ledge 25 by the clamping cleat 24. The free or tail end ofthe felt is passed around the drum and is turned under the edge 16 of the drum at a' time when the camshaft 42 is turned opposite to the position shown in Fig. 3 in order to rotate the felt tensioning bar 35 counter-clockwise into an out-of-the-way inoperative position. After placing the felt around the edge 16 the cam shaft 42 is turned into the position shown in Fig. 3 and the spring 41 forces the teeth 36 of the felt tensioning bar 35 into engagement with the felt to pull it taut as the felt slackens through usage. When operative, the -spring 41 compels the bar 35 to move clockwise and to take up the slack as it is produced.

In placing the abrasive paper upon the roll the paper clamping bar 26 is first moved into an out-of-the-way non-clamping position by rotating the cam shaft 32. This bar automatically carries the paper tensioning arm 46 with it in case it has not been otherwise moved into its out of the way position by rotating its cam shaft 40. The two free ends of the paper are placed in the recess 20 of the flange 19 and the cam shaft 32 is turned into the position shown in Fig. 2 thus causing the spring 31 to force the. paper clamping bar 26 into the recess to clamp the two ends of the paper. l1`he paper is normally placed in the device so that the paper v spans the gap as shown in Fig. 5 in dotted lines. If the cam shaft 40 has been turned to hold the tensioning bar 45 in inoperative position it should then be turned a half revolution to permit the spring 49 to eXert its pressure to bring the parts into tensioning position shown in Fig. 3. However, itis to be observed that the operation of the paper tensioning means by the controlling cam shaft 40 is not necessary since the arrangement of the arm 46 in contiguity with the paper clamping bar 26 causes it to be moved forwardly and rearwardly thereby upon operation of the control shaft 32 of the paper clamping lever. It will be observed by reference to Fig. l that the paper tensioning bar 45 terminates at the point indicated at 55 so that in the successive groups of devices the paper tensioning bars function independently. The endof the adjacent tensioning vision of separate. tension :bars is not vnecessary, but it isl desirable sinceit is likely ,that thev sheet'at, one end ofthe drum ymay stretch lmore than at the other, andthisl arrangementserves to permit any 'onesectionto operate independentlyfof `the `other sections. Further reference to Fig. 1, however, showsthat the felt clamping.. bar' 35' is continuous throughoutI theflength of the drum.fllh`e paper clamping bar 26 is likewise-continuous.

Buty itis to be understood that theseI maybe separated into independent bars similar'to the tensioning bars 1f such` -an Aarrangement 1s preferred.

It will thus be seen that'the invention pro- -bar is indicated'by the numeral-56. The provides suitable clamping andten'sioningstructures for sandingdrums which'` can lbe used singly for small drums or arranged in groups for long drums, and which may be operated by common means fromone end of the drum. I claim as myinvention: n l. In a sanding drum comprising a hollow split cylinder, anl automatic padding take up and tensioning device comprising, in combination, a lever pivoted to move in a plane transverse to the aXis of the drum, a bar carried by said lever and arranged to claw y a sheet of padding entering the gap in the cylinder, and a springy acting on said lever to draw the padding aroundthe cylinder.

2. In a sanding drum comprising a hollow split cylinder, a padding take u and tensioning device comprising, in com ination, a lever pivoted to move in a plane transverse to the aXis of the drum, a bar carriedby said lever and Varranged to take up a sheet of padding entering the gap in the cylinder by placing a yieldabl'e tensioning draw thereon, a spring acting on said lever so to tension and draw the padding, and cam means operable to move said lever into an inoperative position.

3. In a split-surfaced sanding drum, a holding and tensioning device for an abrasive sheet comprising, in combination, a clamping lever and a tensioning lever, each being freely movable transversely to the axis of the drum, spring means operable on each lever, a clamping bar carried by one of said levers, an abutment in the drum against which the spring operated lever presses the clamping bar to clamp the edges of the abrasive sheet causing a portion of the sheet to span the gap in the cylinder, a tensioning bar carried by the other lever and arranged to be Y 4. yIna sandngdrumi of the character 'de'- scribed adapted 'to-have a sheet of padding vbetween anv abrasive Vsheet Vand the drum, means to secure one end of the'padding sheet, ande-automatic slack .taking up and tensioning means for the other end of the sheet.

m5. In a sanding drumof theeharacter described adapted to have a sheet of padding between an abrasive sheet and the drum, means yto :secure one end of each sheet to the drum, automatic means to take up the slack in the padding sheet after passing around the drum,

and other means to tension the abrasive sheet after passing around the drum.

- 6. In a sanding drum Comprising a hollow split cylinder, a sheetA of padding secured at one end vWithinthe cylinder along one side of AthesIOt, and means for clawing the padding mmm' along its opposite edge andl maintaining a vyieldable tensioning draw thereon around the cylinder.r

7. In a sanding drum ofthe character deadapted to havey a sheet of padding between Van abrasive sheet and the drum, the ends of which sheet extend into said slot, means to secure one end of each sheet to the' drum, means Lscribed having a longitudinal slot therein and i tangentially of the drum and across 'the slot. In testimony whereof, I have hereunto afixed my signature.

CHRISTIAN BECKER. 

